This invention relates to an improved spacer for a fiber optic display, that provides improved control over the position and spacing of individual fibers.
Glenn U.S. Pat. Nos. 4,208,096 and 4,116,739 disclose a method for making fiber optic displays that is well suited for large volume, commercial fabrication of displays. In the Glenn method, optical fibers are spirally wrapped around a core spacer, with each layer of fibers separated by a further spacer. The resulting assembly is then split along an angled cut to form two identical displays on each side of the core spacer. The system disclosed in the Glenn patent uses spacers which do not themselves have guides for positioning the fibers laterally across the spacers. Hicks U.S. Pat. No. 3,043,910 shows another fiber optic display that uses flat spacers 27, as best shown in FIG. 12.
Though the Glenn patents describe an effective method that has been successfully used to make fiber optic displays on a commercial basis, there have been efforts to provide spacers with edge guides for fiber optic ribbons. See Sedlmayr U.S. Pat. No. 4,650,280. As shown in FIG. 5 of the Sedlmayr patent, each spacer defines a trough that receives an entire ribbon made up of fiber optic strands positioned in a closely packed arrangement (see also FIG. 2). This approach is severely limited, because the lateral spacing between individual fibers of the ribbon is determined by the ribbon, and not by the spacer itself. This makes it difficult or impossible to alter the lateral spacing between adjacent fiber optic strands with the spacer.
Aurenz U.S. Pat. No. 3,909,109 discloses a fiber optic display in which individual fibers are bent at right angles in the device (FIG. 2). These fibers are mounted on plates 2, which may have embossing to define the position of the fibers (Col. 3, lines 64-66). However, Aurenz provides no details on such embossing, and the right angle bends in the fibers of Aurenz make the structure shown in Aurenz unsuitable for the Glenn fabrication method.
Of course, there has been considerable activity in the field of guiding optical fibers during fabrication of fiber optic devices. Note for example the troughs for receiving rows of closely packed fibers shown in FIG. 11 of James U.S. Pat. No. 3,644,922 and FIGS. 12 and 13 of Yevick U.S. Pat. No. 3,864,034. See also the plates or screens with apertures for individual fibers in Smith U.S. Pat. No. 3,717,531 and Ney U.S. Pat. No. 3,853,658. Comb guides have been used to position individual fibers, as shown in Aurenz U.S. Pat. No. 3,954,546 and Murata U.S. Pat. No. 3,871,591. In a somewhat similar fashion, guides have been provided to separate individual fibers in a cable (Washburn U.S. Pat. No. 3,542,451 and Bloodworth U.S. Pat. No. 4,364,788). Finally, Courtney-Pratt U.S. Pat. No. 3,141,105 and Ogle U.S. Pat. No. 3,498,864 take an entirely different approach by substituting molded arrays of light guides for individual strands that are assembled as described in the Glenn patents.
In spite of the high level of activity in this field, none of the patents discussed above suggests a system for positioning each individual fiber precisely and individually in a display that can be manufactured using the highly advantageous Glenn method.